Watching TV Worse Than Surfing Web

A sedentary lifestyle leads to obesity, speeds up the body's decline and reduces life expectancy. But not all sedentary lifestyles are the same. Sitting at the computer, for example for gaming and surfing the web, does not pose a health risk, say recent studies. Watching TV on the other hand is.

Sports scientists at Queen University in Canada published in BMC Public Health the results of a study in which 2527 children and teenagers aged between 6 and 19 participated. [BMC Public Health. 2011 May 4;11:274.] The researchers noted the participants' exercise pattern and measured their waist circumference, systolic blood pressure and concentration of 'bad cholesterol' and the inflammatory protein CRP in the blood.

The researchers found no relationship between the scores and the amount of time the children and teenagers spent sitting at the computer. The vertical axis represents the likelihood of higher scores.

When they looked at the amount of time the participants spent watching TV each day the researchers did find a relationship. More time spent watching TV was positively correlated with an increased chance of a higher waist circumference, more 'bad cholesterol' and a higher CRP concentration.

The researchers gave the participants a cardio-metabolic risk score based on their waist circumference, systolic blood pressure, 'bad cholesterol' and inflammatory protein CRP concentration in the blood.

The likelihood of a higher score increased for every hour that the children and teenagers spent watching TV daily. Time spent at the computer did not have a negative effect.

The Canadians conclude that parents, government and schools should not only encourage children to get more exercise, but should also discourage TV watching.

Researchers at the National University of Singapore recently published a study with almost identical results in the International Journal of Behavioral Nutrition and Physical Activity. [Int J Behav Nutr Phys Act. 2013 May 30;10:70.] In this study the researchers measured the influence of the number of hours spent each day reading, watching TV, or sitting at the computer on the cardiovascular health of 3305 adults.

Reading and sitting at the computer had no negative effect the researchers discovered. Watching TV did have a negative effect. The figure below shows the relationship between hours spent watching TV, intensive physical exercise and the homeostasis model assessment of insulin resistance [HOMA-IR]: in other words insensitivity to insulin. The more hours the participants spent watching TV each day, the less sensitive their cells were to insulin. Intensive exercise only cancelled out a small amount of that effect.

At the risk of becoming monotonous, a Dutch study was recently published which showed that watching TV is bad for the heart and circulatory system, whereas sitting at the computer is not. [PLoS One. 2013;8(2):e57749.] In that study, where the participants were 634 Dutch people aged between 18 and 28, watching TV led to an increase in triglycerides and insulin in the blood. Computer work did not have this effect.

"Our findings suggest that different types of screen behaviours may have different effects on health outcomes", the researchers write. "Although prospective evidence is needed to confirm a causal relationship, our findings suggest that TV time and computer time should be considered as separated classes of screen behaviour."